Kernel driver not installed (rc=-1908)
The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or there is a permission problem with /dev/vboxdrv.
Please reinstall the kernel module by executing
'/etc/init.d/vboxdrv setup'
as root...
So that I needed to uninstall all of virtualbox packages and install them again. Then, Virtualbox works again.
Sorry for posting many times. As I was able to roll back to original 15.04 as https:/ /wiki.ubuntu. com/Kernel/ MainlineBuilds? action= show&redirect= KernelMainlineB uilds#Uninstall ing_upstream_ kernels instructs. Let me add one comment here that Virtualbox didn't come back again with the following error:
Kernel driver not installed (rc=-1908) init.d/ vboxdrv setup'
The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or there is a permission problem with /dev/vboxdrv.
Please reinstall the kernel module by executing
'/etc/
as root...
So that I needed to uninstall all of virtualbox packages and install them again. Then, Virtualbox works again.